My 08 VDP will occasionally show a yellow warning light and a "Cruise Not Available" message in the display. Is this possibly one of the dreaded aluminum ground studs behind the headlights? Or something totally else? Sometimes I have this all day, sometimes not so much. Not at morning startup, though sometimes pretty soon thereafter.

 

Grounds are always a good place to start on these cars when hunting odd behavior.
Also check your battery voltage. A weak battery will cause these cars to thrown all sorts of random system errors.

The other thing to check is the connector to the Dynamic Stability Control module (ABS unit) as the wheel sensors feed into that first and loss of one or more wheel sensor readings will disable DSC and cruise control.
Check for any obvious corrosion on pins that might need addressing.
The connector pins may also have become a bit tarnished, so using a electrical contact cleaning product (aerosol delivery typically) and inserting the plug repeatedly will help to "scrub" the mating surfaces to rid yourself of any annoying high resistance contacts.

The DSC can also develop poor solder joints internally on the pins of the connector in some cases, but you don't need to go there first........visually look for corrosion or tainted contacts first.

A code reader might also help you determine if you have a bad wheel speed sensor that could be the underlying issue.
Again, could be sensor, cable or intermediate connector issue.

Sorry for the pretty broad response, but these are fairly quick checks and actions that you can do cheaply before broadening the hunt.

 

I had it occasionally, and also "cannot release parkbrake" a little less often. ALWAYS a low voltage issue with mine, like the car had sat for a few days. It has never happened since putting in a new battery.

 

Thanks, very thoughtful. I'll get a to-do list put together for the next rainy day.

 

And in case it was more serious: Jaguar XJ X350 Adaptive Cruise Repair

 

You can have the system programmed to turn off ACC. ACC is a feature of the main CC function. Turning it off will allow CC to function. If the warning light does not continue after doing so, then the ACC unit is the culprit. You can't isolate the ACC unit by simply unplugging it.
Or, jump to the above link to check for corrosion at the ACC radar unit. The radar unit is where I'd place my bet since it's an intermittent problem and known culprit. De-Oxit is a good product to clean corrosion/electrolysis from electronic circuits. I've used it for years to resolve static from vintage stereo equipment dials.

Good Luck with the diagnosis.

Respectfully

 

I've been free of this message for at least 3 days now, and I may try to use CC just to see if anything untoward occurs. I didn't know my cruise was adaptive until just now, when I went out to check. I'd never noticed the rocker switch for gap adjustment before, and I've had the front bumper cover off a couple of times, not noticing a black rectangular blob that would be the radar unit. To do list: 1. see if battery is giving up the ghost, 2. pull the connector from the radar unit to clean the contacts.

Thanks everyone for your sage advice.

 

Pete K,
I replaced the clock spring about 10 years ago, convinced it was the culprit, but alas, it wasn't! Now I have a spare.

I happen to have the bumper cover off for another issue & plan to follow Mark's guidance & look at the ACC unit on the drivers side (U.S.) below the bumper. If it wasn't mentioned above, some have had success by replacing the brake light switch. I would have done that, but so far, I haven't found it!

Hope you can solve the issue in less time than I. Once you find the issue, please share it for I would like to fix it before I kick-out!

Best of luck,

Steve S.